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Metal additive manufacturing is an inherently thermal process, with intense localised heating and for sparse lattice structures, often rapid uneven cooling. Thermal effects influence manufactured geometry through residual stresses and may also result in non-isotropic material properties. This paper aims to increase understanding of the evolution of the temperature field during fabrication of lattice structures through numerical simulation.

This paper uses a reduced order numerical analysis based on “best-practice” compromise found in literature to explore design permutations for lattice structures and provide first-order insight into the effect of these design variables on the temperature field.

Instantaneous and peak temperatures are examined to discover trends at select lattice locations. Insights include the presence of vertical struts reduces overall lattice temperatures by providing additional heat transfer paths; at a given layer, the lower surface of an inclined strut experiences higher temperatures than the upper surface throughout the fabrication of the lattice; during fabrication of the lower layers of the lattice, isolated regions of material can experience significantly higher temperatures than adjacent regions.

Due to the simplifying assumptions and multi-layer material additions, the findings are qualitative in nature. Future research should incorporate additional heat transfer mechanisms.

These findings point towards thermal differences within the lattice which may manifest as dimensional differences and microstructural changes in the built part.

The paper provides qualitative insights into the effect of local geometry and topology upon the evolution of temperature within lattice structures fabricated in metal additive manufacturing.

To develop a numerical method for solving hyperbolic two‐step micro heat transport equations, which have attracted attention in thermal analysis of thin metal films exposed to ultrashort‐pulsed lasers.

An energy estimation for the hyperbolic two‐step model in a three‐dimensional (3D) micro sphere irradiated by ultrashort‐pulsed lasers is first derived, and then a finite difference scheme for solving the hyperbolic two‐step model based on the energy estimation is developed. The scheme is shown to be unconditionally stable and satisfies a discrete analogue of the energy estimation. The method is illustrated by investigating the heat transfer in a micro gold sphere exposed to ultrashort‐pulsed lasers.

Provides information on normalized electron temperature change with time on the surface of the sphere, and shows the changes in electron and lattice temperatures.

The hyperbolic two‐step model is considered under the assumption of constant thermal properties.

A useful tool to investigate the temperature change in a micro sphere irradiated by ultrashort‐pulsed lasers.

Provides a new unconditionally stable finite difference scheme for solving the hyperbolic two‐step model in a 3D micro sphere irradiated by ultrashort‐pulsed lasers.

An energy‐momentum transport model for sub‐micron silicon devices is modified to include new sets of simple interband scattering models representing impact ionization, auger recombination, trapping and photo generation. These have been developed using a simplified physical modelling approach. A discretization scheme suitable for application to an irregular spatial grid is presented. The resulting model is suitable for the study of small geometry effects in silicon devices.

The paper describes the physical phenomena which influence the electrical and mechanical characteristics of low temperature coefficient, high stability thin metal resistive films. Emphasis is placed on the Matthiensen and Arrhenius rules in respect of resistivity and time‐temperature stabilities. The phenomena outlined are highly dependent on the deposition methods used and film properties are discusssed in terms of the film formation kinetics, substrates, and deposition technologies. The production of thin metal film resistive films based on these principles readily achieves temperature coefficients of <5 ppm/°C over the temperature range −55°C to + 155°C with load stress stabilities of <300 ppm with full dissipation, 155°C, 2000 hours, which is as good as bulk nickel‐chromium alloy foil.

An energy balance equation model coupled with drift‐diffusion transport equations are solved in heterojunction p‐i‐n diodes with embedded single quantum well to model hot electron effects. A detailed formulation of hot electron transport is presented. In the well, the carrier energy levels are estimated from the analytical expressions applied to a quantum well with finite height. Both bound and free carriers are modeled by Fermi‐Dirac statistics. Both size quantization and the two dimensional density of states in the well are considered. Thermionic emission is applied to the heterojunctions and quantum wells boundary. Energy transfer among the charge carriers and crystal lattice is modeled by an energy relaxation lifetime. Two sets of devices are simulated. First, the simulated kinetic energy and carrier density profiles were compared with published Monte Carlo results on an GaAs n⁺/n/n⁺ diode. Second, the current‐voltage characteristics of an embedded single quantum well AlGaAs/GaAs p‐i‐n structure was compared with measured data. Both comparisons are satisfactory and demonstrate the usefulness of the model for studying quantum well structures.

The purpose of this paper is to present the multicriteria identification method used for solving the microscale heat transfer problem. The thin film exposed to ultrashort laser pulse is modeled using the finite difference method. The parameters of the model are tuned on the basis of experimental data. The multicriteria identification of the numerical model parameters is performed for subsets of experimental data.

The multicriteria identification method is used in the paper. The Pareto front for two criterions is created. The two-temperature model of heat transfer in microscale is used in the numerical model.

The multicriteria identification for two subsets of experimental data leads to different results. The obtained Pareto front allows to choose the most suitable set of numerical model parameters.

The multicriteria identification method was used for the first time to solve the microscale heat transfer problem.

The purpose of this paper is to set up a consistent off‐equilibrium thermodynamic theory to deal with the self‐heating of electronic nano‐devices.

From the Bloch‐Boltzmann‐Peierls kinetic equations for the coupled system formed by electrons and phonons, an extended hydrodynamic model (HM) has been obtained on the basis of the maximum entropy principle. An electrothermal Monte Carlo (ETMC) simulator has been developed to check the above thermodynamic model.

A 1D n⁺−n−n⁺ silicon diode has been simulated by using the extended HM and the ETMC simulator, confirming the general behaviour.

The paper's analysis is limited to the 1D case. Future researches will also consider 2D realistic devices.

The non‐equilibrium character of electrons and phonons has been taken into account. In previous works, this methodology was used only for equilibrium phonons.

In this paper, the 2‐D numerical analysis is used to investigate the electro‐thermal performance of a trench power VDMOS transistor having a much reduced quasi‐saturation effect over the conventional VDMOS structure. Taking into account all the appropriate physical mechanisms, the analysis self‐consistently solves Poisson's equation, the electron continuity equation and the heat flow equation. The results show that the trench structure introduced enables the device to operate at higher current levels due to a favorable change in current density distribution within the device. However, these two effects can increase the self‐heating of the device, decrease the forward current and degrade the thermal stability of the new structure. Nevertheless the new device is still found to provide a higher quasi‐saturation current than the conventional VDMOS device even when thermal effects are taken into account.

We discuss the device applications of a new impact ionization model. This model is based on a new formulation of the impact ionization rate for bulk semiconductors, derived from solvable high‐field Boltzmann transport equations. The model inputs are relaxation times which simulate the dominant electron‐phonon scatterings and are calibrated by realistic Monte Carlo simulations. Our impact ionization model is shown to be physically motivated and is easily implemented in the standard hydrodynamic device simulators HFIELDS and FIELDAY. An efficient numerical scheme is used to simulate three thin‐base silicon bipolar transistors. Results based on this impact ionization model are found to agree well with the experimental multiplication factors over a large range of applied voltages. These results are contrasted with the more phenomenological treatment of Scholl and Quade which is shown to be a low‐field limit of our model.

Effects of lattice temperature on MOSFET characteristics and a rough distribution of carrier temperature, are studied using a non‐isothermal device simulator which also includes the effect of temperature gradient on the current density. To clarify the mechanism of the increase in lattice temperature, the source of heat generation is investigated. We have confirmed that the increase in lattice temperature results mainly from the generation of Joule heat, representing the product of the electric field and the electron current density. We also found that, as the gate length becomes short, the lattice temperature rises exponentially. In addition, it is found that the lattice temperature shows a localized increase of 77 degrees under normal biasing conditions in the MOSFET with a gate length of 0.5[ μ m].